Extensions of motion-constrained tile sets SEI message for interactivity

ABSTRACT

An extension to the motion-constrained tile sets SEI message provides functionality to signal all tiles are independently decodable and to signal the ROIs that may have more than one tile per ROI. With this extension, the functionality to redefine any independently decodable region-of-interest in a CVS at a coding tree unit level based on user interactivity is enabled. The extension supports the interactivity utilized in various applications such as interactive Ultra High Definition Television (UHDTV), dynamic high-quality zoom-in application, interactive on-demand, e-learning, smart surveillance and many other applications. Additionally, the temporal MCTS SEI message is able to be used by an encoder for tiled streaming to signal explicitly to the decoder that the decoder need only to display the ROI.

CROSS REFERENCE TO RELATED APPLICATION(S)

The present application is a continuation application of U.S. patent application Ser. No. 16/386,552, filed Apr. 17, 2019, which is a continuation application of U.S. patent application Ser. No. 14/331,490, filed Jul. 15, 2014, now U.S. Pat. No. 10,368,078, and claims the benefit of priority from U.S. Provisional Patent Application 61/846,555, filed Jul. 15, 2013, U.S. Provisional Patent Application 61/859,347, filed Jul. 29, 2013, U.S. Provisional Patent Application 61/923,351, filed Jan. 3, 2014, and U.S. Provisional Patent Application 61/928,107, filed Jan. 16, 2014, the entire content of which is hereby incorporated by reference. Each of the above-referenced applications is hereby incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of imaging. More specifically, the present invention relates to video coding.

BACKGROUND OF THE INVENTION

The motion-constrained tile sets in Range Extensions text specification, Draft 3 does not have the functionality to signal all tiles are independently decodable and to signal the Regions of Interest (ROI) that may have more than one tile per ROI.

SUMMARY OF THE INVENTION

An extension to the motion-constrained tile sets SEI message provides functionality to signal all tiles are independently decodable and to signal the ROIs that may have more than one tile per ROI. With this extension, the functionality to redefine any independently decodable region-of-interest in a CVS at a coding tree unit level based on user interactivity is enabled. The extension supports the interactivity utilized in various applications such as interactive Ultra High Definition Television (UHDTV), dynamic high-quality zoom-in application, interactive on-demand, e-learning, smart surveillance and many other applications. Additionally, the temporal MCTS SEI message is able to be used by an encoder for tiled streaming to signal explicitly to the decoder that the decoder need only to display the ROI.

In one aspect, a method programmed in a non-transitory memory of a device comprises receiving a bitstream of a video, wherein the bitstream includes a supplemental enhancement information message, further wherein the supplemental information message signals all tiles are independently decodable and that regions of interest are able to have more than one tile per region of interest and decoding the bitstream on the device. All tiles in a base layer of the video are independently decodable. All tiles in an enhancement layer of the video are independently decodable. Decoding includes providing a mapping of a region of interest in an enhancement layer to the region of interest in a base layer. Decoding includes providing a mapping of a region of interest in a base layer to the region of interest in an enhancement layer. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on the device. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on a second device. A region of interest of the video is selected by a director, wherein the region of interest selected by the director is presented on the device of a user. The video is encoded with independently decodable tiles and in one or more resolution layers and stored on a server. Different users request different resolution layers of the video. Different directors request different resolution layers of the video. The supplemental enhancement information message indicates coding tree blocks outside a selected region of interest, wherein the coding tree blocks outside the selected region of interest are not displayed. The supplemental enhancement information message indicates coding tree blocks outside a selected region of interest, wherein the coding tree blocks outside the selected region of interest are encoded as gray tiles to reduce bitrate.

In another aspect, a system comprises a non-transitory memory configured for storing an application, the application configured for: receiving a bitstream of a video, wherein the bitstream includes a supplemental enhancement information message, further wherein the supplemental information message signals all tiles are independently decodable and that regions of interest are able to have more than one tile per region of interest and decoding the bitstream and a display configured for displaying the decoded bitstream. All tiles in a base layer of the video are independently decodable. All tiles in an enhancement layer of the video are independently decodable. Decoding includes providing a mapping of a region of interest in an enhancement layer to the region of interest in a base layer. Decoding includes providing a mapping of a region of interest in a base layer to the region of interest in an enhancement layer. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on the device. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on a second device. A region of interest of the video is selected by a director, wherein the region of interest selected by the director is presented on the device of a user. The video is encoded with independently decodable tiles and in one or more resolution layers and stored on a server. Different users request different resolution layers of the video. Different directors request different resolution layers of the video. The supplemental enhancement information message indicates coding tree blocks outside a selected region of interest, wherein the coding tree blocks outside the selected region of interest are not displayed. The supplemental enhancement information message indicates coding tree blocks outside a selected region of interest, wherein the coding tree blocks outside the selected region of interest are encoded as gray tiles to reduce bitrate.

In another aspect, an apparatus comprises a non-transitory memory for storing an application, the application for: receiving a bitstream of a video, wherein the bitstream includes a supplemental enhancement information message, further wherein the supplemental information message signals all tiles are independently decodable and that regions of interest are able to have more than one tile per region of interest and decoding the bitstream and a processing component coupled to the memory, the processing component configured for processing the application. All tiles in a base layer of the video are independently decodable. All tiles in an enhancement layer of the video are independently decodable. Decoding includes providing a mapping of a region of interest in an enhancement layer to the region of interest in a base layer. Decoding includes providing a mapping of a region of interest in a base layer to the region of interest in an enhancement layer. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on the device. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on a second device. A region of interest of the video is selected by a director, wherein the region of interest selected by the director is presented on the device of a user. The video is encoded with independently decodable tiles and in one or more resolution layers and stored on a server. Different users request different resolution layers of the video. Different directors request different resolution layers of the video. The supplemental enhancement information message indicates coding tree blocks outside a selected region of interest, wherein the coding tree blocks outside the selected region of interest are not displayed. The supplemental enhancement information message indicates coding tree blocks outside a selected region of interest, wherein the coding tree blocks outside the selected region of interest are encoded as gray tiles to reduce bitrate.

In yet another aspect, a method programmed in a non-transitory memory of a device comprises receiving a bitstream of a video with a base layer and one or more enhancement layers, wherein the bitstream includes a supplemental enhancement information message of an enhancement layer, further wherein the supplemental information message is utilized with inter layer constrained tile sets which can signal all tiles are independently decodable of any other tiles in the layer and that regions of interest have more than one tile per region of interest in the layer; and decoding the bitstream on the device. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on the device. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on a second device. A region of interest of the video is selected by a director, wherein the region of interest selected by the director is presented on the device of a user. Different users request different resolution layers of the video. Different directors request different resolution layers of the video.

In another aspect, a system comprises a non-transitory memory configured for storing an application, the application configured for: receiving a bitstream of a video with a base layer and one or more enhancement layers, wherein the bitstream includes a supplemental enhancement information message of an enhancement layer, further wherein the supplemental information message is utilized with inter layer constrained tile sets which can signal all tiles are independently decodable of any other tiles in the layer and that regions of interest have more than one tile per region of interest in the layer and decoding the bitstream and a display configured for displaying the decoded bitstream. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on the device. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on a second device. A region of interest of the video is selected by a director, wherein the region of interest selected by the director is presented on the device of a user. Different users request different resolution layers of the video. Different directors request different resolution layers of the video.

In another aspect, an apparatus comprises a non-transitory memory for storing an application, the application for: receiving a bitstream of a video with a base layer and one or more enhancement layers, wherein the bitstream includes a supplemental enhancement information message of an enhancement layer, further wherein the supplemental information message is utilized with inter layer constrained tile sets which can signal all tiles are independently decodable of any other tiles in the layer and that regions of interest have more than one tile per region of interest in the layer and decoding the bitstream and a processing component coupled to the memory, the processing component configured for processing the application. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on the device. A region of interest of the video is selected by a user, wherein the region of interest selected by the user is presented on a second device. A region of interest of the video is selected by a director, wherein the region of interest selected by the director is presented on the device of a user. Different users request different resolution layers of the video. Different directors request different resolution layers of the video.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of tiled streaming according to some embodiments.

FIG. 2 illustrates a diagram of re-encoding tiles outside the ROI with minimal bits according to some embodiments.

FIG. 3 illustrates a flowchart of a method of tiled streaming according to some embodiments.

FIG. 4 illustrates a flowchart of a method of tiled streaming according to some embodiments.

FIG. 5 illustrates a flowchart of a method of tiled streaming according to some embodiments.

FIG. 6 illustrates a block diagram of an exemplary computing device configured to implement the tiled streaming method according to some embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In version 1 of the High Efficiency Video Coding (HEVC) standard, when tiles_enabled_flag is equal to 1, each picture is constructed of rectangular regions known as tiles. In the Range Extensions text specification: Draft 3, these tiles are able to be collected to form a collection of tile sets known as Regions of Interest (ROIs). The tile sets are able to be indicated as independently decodable by the motion-constrained tile sets Supplemental Enhancement Information (SEI) messages.

Such HEVC tile structure is able to be applied to interactive tile streaming. An example of tiled streaming is an application where a multi-resolution panorama video is able to be split into videos which are composed of different ROIs and resolutions.

An extension to the motion-constrained tile sets SEI message provides functionality to signal all tiles are independently decodable and to signal the ROIs that may have more than one tile per ROI. With this extension, the functionality to redefine any independently decodable region-of-interest in a Coded Video Stream (CVS) at tile level based on user or director interactivity is enabled. A director is a person who controls content and/or is able to modify the content (e.g., content is modified depending on the group of users it is sent to). The extension supports the interactivity utilized in various applications such as interactive Ultra High Definition Television (UHDTV), dynamic high-quality zoom-in application, interactive on-demand, e-learning, smart surveillance and many other applications.

An ROI is defined as a union of one or more tiles. The extension described herein is used to signal ROIs based on a user or director interactively for a single layer video, or a video with a base layer and at least one enhancement layer. There is a mapping of an ROI in the enhancement layer to an ROI in the base layer. There is also a mapping of an ROI in the base layer to the ROI in the enhancement layer.

The extension described herein signals the motion constrained tile sets for multiple layer video with spatial scalability and/or Signal-to-Noise Ratio (SNR) scalability in the following cases. The motion constrained tile sets with the extension described herein are applied to the enhancement layer (e.g., every tile in the enhancement layer is independently decodable from other tiles in the enhancement layer). Both, the base layer and the enhancement layer, have motion constrained tile sets. Every tile in the base layer is independently decodable. Every tile in the enhancement layer is independently decodable from other tiles in the enhancement layer. A tile in the enhancement layer may depend on one or more tiles in the base layer. There is a mapping of an ROI in the enhancement layer to an ROI in the base layer in the decoding process. There is a mapping of an ROI in the base layer to an ROI in the enhancement layer in the decoding process.

FIG. 1 illustrates a diagram of tiled streaming according to some embodiments. A user is able to interactively select an ROI. After the user selects the ROI, the selected ROI is presented on a device (e.g., television, smart phone, tablet). All of the tiles are independently decodable, since a different user may want a different ROI. It is important to reduce complexity to serve all users by avoiding CTU-level transcoding. In FIG. 1 , a panorama video is encoded with independently decodable tiles and in multiple resolution layers on the server side. One of the resolution layers on the server side is 8K by 4K. Different viewers are able to request the server to send different ROIs from different resolution layers of the panorama video. In FIG. 1 , one client requests a region to be viewed on the client's HD mobile device from one of the resolution layers. Another client requests a different region to be viewed on the client's 4K TV from the same resolution layer. In general, the clients are able to selectively view any ROIs at one of several spatial resolutions. FIG. 1 shows user interactivity with the server at one of the resolution layers.

There are several properties for tiled streaming. All tiles are independently decodable (motion-constrained tiles). The ROIs are not necessarily determined at the beginning of the encode time of a CVS. Once the ROIs are encoded in a CVS, they are able to be modified or re-defined based on user interactivity without re-encoding the CVS at the CTU level.

The motion-constrained tile sets (MCTS) SEI is able to be used to signal the location of independently decodable ROIs. But, in general, MCTS SEI cannot signal the following at the same time: all tiles are independently decodable and the locations of the ROIs. The extension described herein enables MCTS to support all tiles being independently decodable and to signal the locations of the ROIs.

Table 1 shows the MCTS syntax with the extension

Descriptor motion_constrained_tile_sets(payloadSize) { all_tiles_exact_sample_value_match_flag u(1) one_tile_per_tile_set_flag u(1) if (!one_tile_per_tile_set_flag) { num_sets_in_message_minus1 ue(v) for (i=0; i<=num_sets_in_message_minus1; i++) { mcts_id[i] ue(v) num_tile_rects_in_set_minus1[i] ue(v) for (j=0; j<=num_tile_rects_in_set_minus1[i]; j++) { top_left_tile_index [i][j] ue(v) bottom_right_tile_index[i][j] ue(v) } if(!all_tiles_exact_sample_value_match_flag) { exact_sample_value_match_flag[i] u(1) } } } } The all_tiles_exact_sample_value_match_flag is similar to the definition of exact_sample_value_match_flag for a motion-constrained tile set, but applies to every tile. all_tiles_exact_sample_value_match_flag equal to 0 indicates that within the coded video sequence, when the coding tree blocks are outside a motion constrained tile set are not decoded and the boundaries of the motion constrained tile set are treated as picture boundaries for purposes of the decoding process, the value of each sample in the motion constrained tile set may not be exactly the same as the value of the same sample when all of the coding tree blocks of the picture are decoded. The all_tiles_exact_sample_value_match_flag equal to 1 indicates that within the coded video sequence, when the coding tree blocks that do not belong to a motion constrained tile set are not decoded and the boundaries of the motion constrained tile set are treated as picture boundaries for purposes of the decoding process, the value of each sample in the motion constrained tile set would be exactly the same as the value of the sample that would be obtained when all the coding tree blocks of all pictures in the coded video sequence are decoded. one_tile_per_tile_set_flag equal to 1 indicates that each tile forms a tile set.

A similar extension to the motion-constrained tile sets SEI message is also able to be applied to the inter layer constrained tile sets (ILCTS) in JCTVC-N0087. In particular, the syntax of JCTVC-N0087 for interlayer does not have the capability to signal ROIs when every tile is a tile set, and it is extended as in Table 2.

Inter Layer Constrained Tile Sets

Table 2 Shows Modified Inter-Layer Syntax

Descriptor inter_layer_constrained_tile_sets(payloadSize) { il_all_tiles_exact_sample_value_match_flag u(1) il_one_tile_per_tile_set_flag u(1) if (!il_one_tile_per_tile_set_flag) { il_num_sets_in_message_minus1 ue(v) if(il_num_sets_in_message_minus1) skipped_tile_set_present_flag u(1) numSignificantSets = il_num_sets_in_message_minus1 − skipped_tile_set_present_flag + 1 for (i=0; i<numSignificantSets; i++) { ilcts_id[i] ue(v) il_num_tile_rects_in_set_minus1[i] ue(v) for (j=0; j<=il_num_tile_rects_in_set_minus1[i]; j++) { il_top_left_tile_index [i][j] ue(v) il_bottom_right_tile_index[i][j] ue(v) } ilc_idc[i] u(2) if(!il_all_tiles_exact_sample_value_match_flag) { il_exact_sample_value_match_flag[i] u(1) } } else all_tiles_ilc_idc u(2) } The scope of the inter-layer constrained tile sets SEI message is a complete CLVS of the layer with nuh_layer_id equal to targetLayerId. When an inter-layer tile sets SEI message is present for any coded picture of a CLVS and the first coded picture of the CLVS in decoding order is an IRAP picture, the inter-layer tile sets SEI message shall be present for the first coded picture of the CLVS in decoding order and may also be present for other coded pictures of the CLVS.

The inter-layer constrained tile sets SEI message shall not be present for the layer with nuh_layer_id equal to targetLayerId when tiles_enabled_flag is equal to 0 for any PPS that is active for the layer.

The inter-layer constrained tile sets SEI message shall not be present for the layer with nuh_layer_id equal to targetLayerId unless every PPS that is active for the pictures of the CLVS of the layer with nuh_layer_id equal to targetLayerId has tile_boundaries_aligned_flag equal to 1 or fulfills the conditions that would be indicated by tile_boundaries_aligned_flag being equal to 1.

An identified tile set is defined as a set of tiles within a picture with nuh_layer_id targetLayerId that contains the tiles specified below on the basis of the values of the syntax elements contained in the inter-layer constrained tile sets SEI message.

An associated reference tile set for the iPred-th identified tile set with ilcts_id[iPred] equal to ilctsId, if any, is defined as the identified tile set present in the same access unit as the iPred-th identified tile set and associated with ilcts_id[iRef] equal to ilctsId and nuh_layer_id equal to RefLayerId[targetLayerId][j] for any value of j in the range of 0 to NumDirectRefLayers[targetLayerId]−1, inclusive.

The presence of the inter-layer constrained tile sets SEI message indicates that the inter-layer prediction process is constrained such that no sample value outside each associated reference tile set, and no sample value at a fractional sample position that is derived using one or more sample values outside each associated reference tile set, is used for inter-layer prediction of any sample within the identified tile set.

When loop filtering and resampling filter is applied across tile boundaries, inter-layer prediction of any samples within an identified tile set that refers to samples within 8 samples from an associated reference tile set boundary that is not also a picture boundary may result in propagation of mismatch error. An encoder can avoid such potential error propagation by avoiding the use of motion vectors that cause such references.

When more than one inter-layer constrained tile sets SEI message is present for a CLVS, they shall contain identical content.

The number of inter-layer constrained tile sets SEI messages for the same CLVS in each access unit shall not exceed 5.

il_all_tiles_exact_sample_value_match_flag equal to equal to 1 indicates that, within the CLVS, when the coding tree blocks that are outside of any tile in any identified tile set specified in this inter-layer constrained tile sets SEI message are not decoded and the boundaries of the tile is treated as picture boundaries for purposes of the decoding process, the value of each sample in the tile would be exactly the same as the value of the sample that would be obtained when all the coding tree blocks of all pictures in the CLVS are decoded.

il_all_tiles_exact_sample_value_match_flag equal to 0 indicates that, within the CLVS, when the coding tree blocks that are outside of any tile in any identified tile set specified in this inter-layer constrained tile sets SEI message are not decoded and the boundaries of the tile is treated as picture boundaries for purposes of the decoding process, the value of each sample in the tile may or may not be exactly the same as the value of the same sample when all the coding tree blocks of all pictures in the CLVS are decoded.

il_one_tile_per_tile_set_flag equal to 1 indicates that each identified tile set contains one tile, and il_num_sets_in_message_minus1 is not present. When il_one_tile_per_tile_set_flag is equal to 1, the following applies:

-   -   (num_tile_columns_minus1+1)*(num_tile_rows_minus1+1) shall be         less than or equal to 256.

The value of ilcts_id[i] for the i-th tile in tile raster scan order in the range of 0 to (num_tile_columns_minus1+1)*(num_tile_rows_minus1+1)−1, inclusive, is inferred to be equal to 256+i.

When il_one_tile_per_tile_set_flag is equal to 0, the identified tile sets are signalled explicitly. il_num_sets_in_message_minus1 plus 1 specifies the number of inter-layer identified tile sets in the SEI message. The value of il_num_sets_in_message_minus1 shall be in the range of 0 to 255, inclusive.

skipped_tile_set_present_flag equal to 1 indicates that, within the CLVS, the il_num_sets_in_message_minus1-th identified tile set consists of those remaining tiles that are not included in any earlier identified tile sets in the same message and all the prediction blocks that are inside the il_num_sets_in_message_minus1-th identified tile set are inter-layer predicted from inter-layer reference pictures with nuh_layer_id equal to RefLayerId[targetLayerId][NumDirectRefLayers[targetLayerId]−1] and no residual_coding( ) syntax structure is present in any transform unit of the il_num_sets_in_message_minus1-th identified tile set.

skipped_tile_set_present_flag equal to 0 does not indicate a bitstream constraint within the CLVS. When not present, the value of skipped_tile_set_present_flag is inferred to be equal to 0. ilcts_id[i] contains an identifying number that may be used to identify the purpose of the i-th identified tile set (for example, to identify an area to be extracted from the coded video sequence for a particular purpose). The value of ilcts_id[i] shall be in the range of 0 to 2³²−2, inclusive. Values of ilcts_id[i] from 0 to 255, inclusive, and from 512 to 2³¹−1, inclusive, may be used as determined by the application. If il_one_tile_per_tile_set_flag is equal to 1, values of ilcts_id[i] from 256 to 511, inclusive are used for the inferred ilcts_id[i] values as specified above. Otherwise, values of ilcts_id[i] from 256 to 511, inclusive, are reserved for future use by ITU-T ¦ISO/IEC. Values of ilcts_id[i] from 2³¹ to 2³²−2, inclusive, are reserved for future use by ITU-T ¦ ISO/IEC. Decoders encountering an indicated value of ilcts_id[i] in the range of 256 to 511, inclusive, or in the range of 2³¹ to 2³²−2, inclusive, shall ignore (remove from the bitstream and discard) it.

il_num_tile_rects_in_set_minus1[i] plus 1 specifies the number of rectangular regions of tiles in the i-th identified tile set. The value of il_num_tile_rects_in_set_minus1 [i] shall be in the range of 0 to (num_tile_columns_minus1+1)*(num_tile_rows_minus1+1)−1, inclusive. il_top_left_tile_index[i][j] and il_bottom_right_tile_index[i][j] identify the tile position of the top-left tile and the tile position of the bottom-right tile in a rectangular region of the i-th identified tile set, respectively, in tile raster scan order.

ilc_idc[i] equal to 1 indicates that no samples outside of the any associated reference tile set and no samples at a fractional sample position that is derived using one or more samples outside of any associated reference tile set are used for inter-layer prediction of any sample within.

ilc_idc[i] equal to 2 indicates that no prediction block in the i-th identified tile set is predicted from an inter-layer reference picture. ilc_idc[i] equal to 0 indicates that the inter-layer prediction process may or may not be constrained for the prediction block in the i-th identified tile set. The value of ilc_idc[i] equal to 3 is reserved.

il_exact_sample_value_match_flag[i] equal to 1 indicates that, within the CLVS, when the coding tree blocks that do not belong to the i-th identified tile set are not decoded and the boundaries of the i-th identified tile set are treated as picture boundaries for the purposes of the decoding process, the value of each sample in the i-th identified tile set would be exactly the same as the value of the sample that would be obtained when all the coding tree blocks of all pictures in the CLVS are decoded. il_exact_sample_value_match_flag[i] equal to 0 indicates that, within the CLVS, when the coding tree blocks that are outside of the i-th identified inter-layer constrained tile set are not decoded and the boundaries of the i-th identified tile set are treated as picture boundaries for the purposes of the decoding process, the value of each sample in the i-th identified tile set may or may not be exactly the same as the value of the same sample when all the coding tree blocks of all pictures in the CLVS are decoded.

It is feasible to use il_exact_sample_value_match_flag equal to 1 when using certain combinations of loop_filter_across_tiles_enabled_flag, pps_loop_filter_across_slices_enabled_flag, pps_deblocking_filter_disabled_flag, slice_loop_filter_across_slices_enabled_flag, slice_deblocking_filter_disabled_flag, sample_adaptive_offset_enabled_flag, slice_sao_luma_flag, and slice_sao_chroma_flag. all_tiles_ilc_idc equal to 1 indicates that, for each identified tile set within the CLVS, no sample value outside of each associated reference tile set and no sample value at a fractional sample position that is derived using one or more samples outside of each associated reference tile set is used for inter-layer prediction of any sample within the identified tile set. all_tiles_ilc_idc equal to 2 indicates that, within the CLVS, no prediction block in each identified tile set is predicted from an inter-layer reference picture. all_tiles_ilc_idc equal to 0 indicates that, within the CLVS, the inter-layer prediction process may or may not be constrained for the identified tile sets. The value of all_tiles_ilc_idc equal to 3 is reserved. When all_tiles_ild_idc is not present, it is inferred to be equal to 0.

Temporal Motion Constrained Tile Sets (Temporal MCTS)

The temporal motion constrained tile sets (Temporal MCTS) SEI message in JCTVC-O1005 is able to be extended to signal that the coding tree blocks outside of the ROI should not be displayed. With this extension, the temporal motion constrained tile sets SEI message is able to be used by an encoder for tiled streaming to signal explicitly to the decoder that the decoder need only to display the ROI. The Temporal MCTS SEI message is able to be used for tile streaming. For the example of tiled streaming, a panorama video is encoded in the server side with independently decodable tiles, only a subset of the tiles is requested by the client decoder as ROI by gray tiles (or tiles that are able to be encoded very efficiently such as low bitrate content) and signal the decoder not to display the gray tiles (or the efficiently coded tiles).

When a decoder receives the modified Temporal MCTS SEI messages that signal not to display outside the ROI, the decoder is able to choose to: 1) not display the area outside the ROI, 2) replace the area outside the ROI with a pre-determined color. The color is able to be used for chroma keying for displaying with other content.

FIG. 2 illustrates a panorama video is encoded on the server side with independently decodable tiles, only a subset of the tiles is requested by the client decoder as ROI for display purposes. To reduce transmission bandwidth, the server is able to replace the tiles outside the ROI with gray tiles and signal the decoder not to display the gray tiles. Further, different clients are able to request different ROIs to be streamed from the server.

The temporal MCTS SEI message is able to be modified in a number of ways. Several possible embodiments are described herein. In some embodiments, whether to display the coding tree blocks outside the ROIs is signaled in a bitstream.

Table 3 shows the modified syntax of a temporal motion constrained tile sets function.

Descriptor temporal_motion_constrained_tile_sets(payloadSize) { mc_all_tiles_exact_sample_value_match_flag u(1) each_tile_one_tile_set_flag u(1) display_tile_sets_only_flag u(1) if (!each_tile_one_tile_set_flag) { num_sets_in_message_minus1 ue(v) for (i=0; i<=num_sets_in_message_minus1; i++) { mcts_id[i] ue(v) num_tile_rects_in_set_minus1[i] ue(v) for (j=0; j<=num_tile_rects_in_set_minus1[i]; j++) { top_left_tile_index [i][j] ue(v) bottom_right_tile_index[i][j] ue(v) } if(!mc_all_tiles_exact_sample_value_match_flag) { exact_sample_value_match_flag[i] u(1) } } } Display_tile_sets_only_flag equal to 1 specifies that all coding tree blocks in all tile sets should be displayed and all coding tree blocks not in any tile set should not be displayed.

Display tile set only flag equal to 0 indicates that this flag should be ignored.

Table 4 shows the modified syntax of a temporal motion constrained tile sets function.

Descriptor temporal_motion_constrained_tile_sets(payloadSize) { mc_all_tiles_exact_sample_value_match_flag u(1) each_tile_one_tile_set_flag u(1) no_display_outside_tile_sets_flag u(1) if (!each_tile_one_tile_set_flag) { num_sets_in_message_minus1 ue(v) for (i=0; i<=num_sets_in_message_minus1; i++) { mcts_id[i] ue(v) num_tile_rects_in_set_minus1[i] ue(v) for (j=0; j<=num_tile_rects_in_set_minus1[i]; j++) { top_left_tile_index [i][j] ue(v) bottom_right_tile_index[i][j] ue(v) } if(!mc_all_tiles_exact_sample_value_match_flag) { exact_sample_value_match_flag[i] u(1) } } } no_display_outside_tile_sets_flag equal to 1 specifies that all coding tree blocks not in any tile set should not be displayed. no_display_outside_tile_sets_flag equal to 0 indicates that this flag should be ignored.

In some embodiments, the syntax of temporal_motion_constrained_tile_sets and the inter_layer_constrained_tile_sets are aligned. In particular, the no_display_last_tile_set_flag plays a parallel role to the skipped_tile_set_present_flag in the inter_layer_constrained_tile_sets SEI message.

Table 5 shows the modified syntax of a temporal motion constrained tile sets function.

Descriptor temporal_motion_constrained_tile_sets(payloadSize) { mc_all_tiles_exact_sample_value_match_flag u(1) each_tile_one_tile_set_flag u(1) if (!each_tile_one_tile_set_flag) { num_sets_in_message_minus1 ue(v) if(num_sets_in_message_minus1) no_display_last_tile_set_flag u(1) numSignificantSets = num_sets_in_message_minus1 − non_signficant_tile_set_present_flag + 1 for (i=0; i<=numSignificantSets; i++) { mcts_id[i] ue(v) num_tile_rects_in_set_minus1[i] ue(v) for (j=0; j<=num_tile_rects_in_set_minus1[i]; j++) { top_left_tile_index [i][j] ue(v) bottom_right_tile_index[i][j] ue(v) } if(!mc_all_tiles_exact_sample_value_match_flag) { exact_sample_value_match_flag[i] u(1) } } } no_display_last_tile_set_flag equal to 1 specifies that the last tile includes those tiles that are not included in any earlier tile sets in the same message and the last tile should not be displayed. no_display_last_tile_set_flag equal to 0 indicates that the last tile set may or may not include those tiles that are not included in any earlier tile sets in the same message.

In some embodiments, only a single tile set is displayed.

Table 6 shows the modified syntax of a temporal motion constrained tile sets function.

Descriptor temporal_motion_constrained_tile_sets(payloadSize) { mc_all_tiles_exact_sample_value_match_flag u(1) each_tile_one_tile_set_flag u(1) if (!each_tile_one_tile_set_flag) { num_sets_in_message_minus1 ue(v) for (i=0; i<=num_sets_in_message_minus1; i++) { mcts_id[i] ue(v) num_tile_rects_in_set_minus1[i] ue(v) for (j=0; j<=num_tile_rects_in_set_minus1[i]; j++) { top_left_tile_index [i][j] ue(v) bottom right tile index[i][j] ue(v) } if(!mc_all_tiles_exact_sample_value_match_flag) { exact_sample_value_match_flag[i] u(1) } } single_tile_set_display_flag u(1) if(single_tile_set_display_flag) display_tile_set_idc ue(v) } single_tile_set_display_flag equal to 1 specifies that the display_tile_set_idc syntax element is present. single_tile_set_display_flag equal to 0 specifies that the display_tile_set_idc syntax element is not present.

display_tile_set_idc, when present, indicates that only the display_tile_set_idc-th tile set is intended for display. display_tile_set_idc shall be in the range of 0 to num_sets_in_message_minus1.

Table 7 shows the modified syntax of a temporal motion constrained tile sets function.

Descriptor temporal_motion_constrained_tile_sets(payloadSize) { mc_all_tiles_exact_sample_value_match_flag u(1) each_tile_one_tile_set_flag u(1) if (!each_tile_one_tile_set_flag) { limited_tile_set_display_flag u(1) num_sets_in_message_minus1 ue(v) for (i=0; i<=num_sets_in_message_minus1; i++) { mcts_id[i] ue(v) if (limited tile set display flag) display_tile_set_flag[i] num_tile_rects_in_set_minus1[i] ue(v) for (j=0; j<=num_tile_rects_in_set_minus1[i]; j++) { top_left_tile_index [i][j] ue(v) bottom_right_tile_index[i][j] ue(v) } if(!mc_all_tiles_exact_sample_value_match_flag) { exact_sample_value_match_flag[i] u(1) } } } limited_tile_set_display flag equal to 1 specifies that the display tile_set_flag[i] syntax element is present and indicates that the tiles not included within any tile set with display_tile_set_flag[i] equal to 1 are not intended for display. limited_tile_set_display flag equal to 0 specifies that the display_tile_set_flag[i] syntax element is not present.

display_tile_set_flag[i] equal to 1 indicates that the i-th tile set is intended for display. display_tile_set_flag[i] equal to 0 indicatest that the i-th tile set is not intended for display. When not present, the value of display_tile_set_flag[i] is inferred to be equal to 1.

FIG. 3 illustrates a flowchart of a method of tiled streaming according to some embodiments. In the step 300, a video bitstream is transmitted from a device (e.g., server) to a second device (e.g., television). The video bitstream includes an SEI message with the extensions described herein. The SEI message is capable of signaling that all tiles are independently decodable of other tiles. In the step 302, the video bistream is decoded. In the step 304, the decoded video is displayed. In the step 306, a user selects an ROI of the video for interactivity purposes. In the step 308, the selected ROI is presented to the user. In some embodiments, fewer or additional steps are implemented. In some embodiments, the order of the steps is modified.

FIG. 4 illustrates a flowchart of a method of tiled streaming according to some embodiments. In the step 400, locations of ROIs are signaled in an MCTS SEI message. In the step 402, an ROI in the base layer is mapped to an ROI in the enhancement layer in the video decoding process. In the step 404, each tile in the enhancement layer is decoded independent from other tiles in the MCTS of the enhancement layer. In some embodiments, fewer or additional steps are implemented.

FIG. 5 illustrates a flowchart of a method of tiled streaming according to some embodiments. In the step 500, the decoder is signaled as to which ROIs are not to be displayed. In the step 502, the decoder is signaled as to which ROIs are to be displayed (e.g., an ROI selected by a user). In the step 504, tiles outside the ROI to be displayed are replaced with gray tiles to reduce bandwidth. In the step 506, SEI messages are generated to signal locations of coding tree blocks outside temporal motion constrained tile sets. In some embodiments, fewer or additional steps are implemented. In some embodiments, steps of FIGS. 3, 4 and 5 are able to be implemented together. For example, although the step 500 is shown in FIG. 5 , the step 500 is able to be implemented with the steps of FIG. 3 .

FIG. 6 illustrates a block diagram of an exemplary computing device configured to implement the tiled streaming method according to some embodiments. The computing device 600 is able to be used to acquire, store, compute, process, communicate and/or display information such as images and videos. In general, a hardware structure suitable for implementing the computing device 600 includes a network interface 602, a memory 604, a processor 606, I/O device(s) 608, a bus 610 and a storage device 612. The choice of processor is not critical as long as a suitable processor with sufficient speed is chosen. The memory 604 is able to be any conventional computer memory known in the art. The storage device 612 is able to include a hard drive, CDROM, CDRW, DVD, DVDRW, High Definition disc/drive, ultra-HD drive, flash memory card or any other storage device. The computing device 600 is able to include one or more network interfaces 602. An example of a network interface includes a network card connected to an Ethernet or other type of LAN. The I/O device(s) 608 are able to include one or more of the following: keyboard, mouse, monitor, screen, printer, modem, touchscreen, button interface and other devices. Tiled streaming application(s) 630 used to perform the tiled streaming method are likely to be stored in the storage device 612 and memory 604 and processed as applications are typically processed. More or fewer components shown in FIG. 6 are able to be included in the computing device 600. In some embodiments, tiled streaming hardware 620 is included. Although the computing device 600 in FIG. 6 includes applications 630 and hardware 620 for the tiled streaming method, the tiled streaming method is able to be implemented on a computing device in hardware, firmware, software or any combination thereof. For example, in some embodiments, the tiled streaming applications 630 are programmed in a memory and executed using a processor. In another example, in some embodiments, the tiled streaming hardware 620 is programmed hardware logic including gates specifically designed to implement the tiled streaming method.

In some embodiments, the tiled streaming application(s) 630 include several applications and/or modules. In some embodiments, modules include one or more sub-modules as well. In some embodiments, fewer or additional modules are able to be included.

Examples of suitable computing devices include a personal computer, a laptop computer, a computer workstation, a server, a mainframe computer, a handheld computer, a personal digital assistant, a cellular/mobile telephone, a smart appliance, a gaming console, a digital camera, a digital camcorder, a camera phone, a smart phone, a portable music player, a tablet computer, a mobile device, a video player, a video disc writer/player (e.g., DVD writer/player, high definition disc writer/player, ultra high definition disc writer/player), a television, a home entertainment system, smart jewelry (e.g., smart watch) or any other suitable computing device.

To utilize the tiled streaming method, a device such as a digital video camera is able to be used to acquire a video. The tiled streaming method is automatically implemented during or after acquiring a video such as during playback of the video. The tiled streaming method is able to be implemented automatically without user involvement.

In operation, the tiled streaming method enables users to interactively select portions of an image/video. The extension supports the interactivity utilized in various applications such as interactive Ultra High Definition Television (UHDTV), dynamic high-quality zoom-in application, interactive on-demand, e-learning, smart surveillance and many other applications.

Some Embodiments of Extensions of Motion-Constrained Tile Sets SEI Message for Interactivity

-   1. A method programmed in a non-transitory memory of a device     comprising:     -   a. receiving a bitstream of a video, wherein the bitstream         includes a supplemental enhancement information message, further         wherein the supplemental information message signals all tiles         are independently decodable and that regions of interest are         able to have more than one tile per region of interest; and     -   b. decoding the bitstream on the device. -   2. The method of clause 1 wherein all tiles in a base layer of the     video are independently decodable. -   3. The method of clause 1 wherein all tiles in an enhancement layer     of the video are independently decodable. -   4. The method of clause 1 wherein decoding includes providing a     mapping of a region of interest in an enhancement layer to the     region of interest in a base layer. -   5. The method of clause 1 wherein decoding includes providing a     mapping of a region of interest in a base layer to the region of     interest in an enhancement layer. -   6. The method of clause 1 wherein a region of interest of the video     is selected by a user, wherein the region of interest selected by     the user is presented on the device. -   7. The method of clause 1 wherein a region of interest of the video     is selected by a user, wherein the region of interest selected by     the user is presented on a second device. -   8. The method of clause 1 wherein a region of interest of the video     is selected by a director, wherein the region of interest selected     by the director is presented on the device of a user. -   9. The method of clause 1 wherein the video is encoded with     independently decodable tiles and in one or more resolution layers     and stored on a server. -   10. The method of clause 1 wherein different users request different     resolution layers of the video. -   11. The method of clause 1 wherein different directors request     different resolution layers of the video. -   12. The method of clause 1 wherein the supplemental enhancement     information message indicates coding tree blocks outside a selected     region of interest, wherein the coding tree blocks outside the     selected region of interest are not displayed. -   13. The method of clause 1 wherein the supplemental enhancement     information message indicates coding tree blocks outside a selected     region of interest, wherein the coding tree blocks outside the     selected region of interest are encoded as gray tiles to reduce     bitrate. -   14. A system comprising:     -   a. a non-transitory memory configured for storing an         application, the application configured for:         -   i. receiving a bitstream of a video, wherein the bitstream             includes a supplemental enhancement information message,             further wherein the supplemental information message signals             all tiles are independently decodable and that regions of             interest are able to have more than one tile per region of             interest; and         -   ii. decoding the bitstream; and     -   b. a display configured for displaying the decoded bitstream. -   15. The system of clause 14 wherein all tiles in a base layer of the     video are independently decodable. -   16. The system of clause 14 wherein all tiles in an enhancement     layer of the video are independently decodable. -   17. The system of clause 14 wherein decoding includes providing a     mapping of a region of interest in an enhancement layer to the     region of interest in a base layer. -   18. The system of clause 14 wherein decoding includes providing a     mapping of a region of interest in a base layer to the region of     interest in an enhancement layer. -   19. The system of clause 14 wherein a region of interest of the     video is selected by a user, wherein the region of interest selected     by the user is presented on the device. -   20. The system of clause 14 wherein a region of interest of the     video is selected by a user, wherein the region of interest selected     by the user is presented on a second device. -   21. The system of clause 14 wherein a region of interest of the     video is selected by a director, wherein the region of interest     selected by the director is presented on the device of a user. -   22. The system of clause 14 wherein the video is encoded with     independently decodable tiles and in one or more resolution layers     and stored on a server. -   23. The system of clause 14 wherein different users request     different resolution layers of the video. -   24. The system of clause 14 wherein different directors request     different resolution layers of the video. -   25. The system of clause 14 wherein the supplemental enhancement     information message indicates coding tree blocks outside a selected     region of interest, wherein the coding tree blocks outside the     selected region of interest are not displayed. -   26. The system of clause 14 wherein the supplemental enhancement     information message indicates coding tree blocks outside a selected     region of interest, wherein the coding tree blocks outside the     selected region of interest are encoded as gray tiles to reduce     bitrate. -   27. An apparatus comprising:     -   a. a non-transitory memory for storing an application, the         application for:         -   i. receiving a bitstream of a video, wherein the bitstream             includes a supplemental enhancement information message,             further wherein the supplemental information message signals             all tiles are independently decodable and that regions of             interest are able to have more than one tile per region of             interest; and         -   ii. decoding the bitstream; and     -   b. a processing component coupled to the memory, the processing         component configured for processing the application. -   28. The apparatus of clause 27 wherein all tiles in a base layer of     the video are independently decodable. -   29. The apparatus of clause 27 wherein all tiles in an enhancement     layer of the video are independently decodable. -   30. The apparatus of clause 27 wherein decoding includes providing a     mapping of a region of interest in an enhancement layer to the     region of interest in a base layer. -   31. The apparatus of clause 27 wherein decoding includes providing a     mapping of a region of interest in a base layer to the region of     interest in an enhancement layer. -   32. The apparatus of clause 27 wherein a region of interest of the     video is selected by a user, wherein the region of interest selected     by the user is presented on the device. -   33. The apparatus of clause 27 wherein a region of interest of the     video is selected by a user, wherein the region of interest selected     by the user is presented on a second device. -   34. The apparatus of clause 27 wherein a region of interest of the     video is selected by a director, wherein the region of interest     selected by the director is presented on the device of a user. -   35. The apparatus of clause 27 wherein the video is encoded with     independently decodable tiles and in one or more resolution layers     and stored on a server. -   36. The apparatus of clause 27 wherein different users request     different resolution layers of the video. -   37. The apparatus of clause 27 wherein different directors request     different resolution layers of the video. -   38. The apparatus of clause 27 wherein the supplemental enhancement     information message indicates coding tree blocks outside a selected     region of interest, wherein the coding tree blocks outside the     selected region of interest are not displayed. -   39. The apparatus of clause 27 wherein the supplemental enhancement     information message indicates coding tree blocks outside a selected     region of interest, wherein the coding tree blocks outside the     selected region of interest are encoded as gray tiles to reduce     bitrate. -   40. A method programmed in a non-transitory memory of a device     comprising:     -   a. receiving a bitstream of a video with a base layer and one or         more enhancement layers, wherein the bitstream includes a         supplemental enhancement information message of an enhancement         layer, further wherein the supplemental information message is         utilized with inter layer constrained tile sets which can signal         all tiles are independently decodable of any other tiles in the         layer and that regions of interest have more than one tile per         region of interest in the layer; and     -   b. decoding the bitstream on the device. -   41. The method of clause 40 wherein a region of interest of the     video is selected by a user, wherein the region of interest selected     by the user is presented on the device. -   42. The method of clause 40 wherein a region of interest of the     video is selected by a user, wherein the region of interest selected     by the user is presented on a second device. -   43. The method of clause 40 wherein a region of interest of the     video is selected by a director, wherein the region of interest     selected by the director is presented on the device of a user. -   44. The method of clause 40 wherein different users request     different resolution layers of the video. -   45. The method of clause 40 wherein different directors request     different resolution layers of the video. -   46. A system comprising:     -   a. a non-transitory memory configured for storing an         application, the application configured for:         -   i. receiving a bitstream of a video with a base layer and             one or more enhancement layers, wherein the bitstream             includes a supplemental enhancement information message of             an enhancement layer, further wherein the supplemental             information message is utilized with inter layer constrained             tile sets which can signal all tiles are independently             decodable of any other tiles in the layer and that regions             of interest have more than one tile per region of interest             in the layer; and         -   ii. decoding the bitstream; and     -   b. a display configured for displaying the decoded bitstream. -   47. The system of clause 46 wherein a region of interest of the     video is selected by a user, wherein the region of interest selected     by the user is presented on the device. -   48. The system of clause 46 wherein a region of interest of the     video is selected by a user, wherein the region of interest selected     by the user is presented on a second device. -   49. The system of clause 46 wherein a region of interest of the     video is selected by a director, wherein the region of interest     selected by the director is presented on the device of a user. -   50. The system of clause 46 wherein different users request     different resolution layers of the video. -   51. The system of clause 46 wherein different directors request     different resolution layers of the video. -   52. An apparatus comprising:     -   a. a non-transitory memory for storing an application, the         application for:         -   i. receiving a bitstream of a video with a base layer and             one or more enhancement layers, wherein the bitstream             includes a supplemental enhancement information message of             an enhancement layer, further wherein the supplemental             information message is utilized with inter layer constrained             tile sets which can signal all tiles are independently             decodable of any other tiles in the layer and that regions             of interest have more than one tile per region of interest             in the layer; and         -   ii. decoding the bitstream; and     -   b. a processing component coupled to the memory, the processing         component configured for processing the application. -   53. The system of clause 52 wherein a region of interest of the     video is selected by a user, wherein the region of interest selected     by the user is presented on the device. -   54. The system of clause 52 wherein a region of interest of the     video is selected by a user, wherein the region of interest selected     by the user is presented on a second device. -   55. The system of clause 52 wherein a region of interest of the     video is selected by a director, wherein the region of interest     selected by the director is presented on the device of a user. -   56. The system of clause 52 wherein different users request     different resolution layers of the video. -   57. The system of clause 52 wherein different directors request     different resolution layers of the video.

The present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of principles of construction and operation of the invention. Such reference herein to specific embodiments and details thereof is not intended to limit the scope of the claims appended hereto. It will be readily apparent to one skilled in the art that other various modifications may be made in the embodiment chosen for illustration without departing from the spirit and scope of the invention as defined by the claims. 

What is claimed is:
 1. An apparatus, comprising: circuitry configured to: decode an encoded bitstream of a video; and generate an image of a region based on information which indicates whether a value of each sample in a motion constrained tile set is the same as a value of a sample obtained in a case where all coding tree blocks of all pictures are decoded, and in a case where boundaries of the motion constrained tile set are treated as picture boundaries for the decoding, and the coding tree blocks that do not belong to the motion constrained tile set are not decoded, wherein the encoded bitstream includes the information, the information further indicates that an area outside the region is not to be displayed, the information includes one flag that applies to every tile, the information further includes flag information that indicates whether a last tile set includes a plurality of tiles that are not included in previous tile sets in a same message, and the last tile set is not be displayed, and the previous tile sets are specified prior to the last tile set.
 2. The apparatus according to claim 1, wherein the information is included in a supplemental enhancement information message of the encoded bitstream.
 3. The apparatus according to claim 1, wherein the circuitry is configured to control reception the encoded bitstream including a supplemental enhancement information message.
 4. The apparatus according to claim 1, wherein the circuitry is further configured to generate the image of the region including one or more tiles.
 5. The apparatus according to claim 4, wherein the region includes the one or more tiles based on user selection.
 6. The apparatus according to claim 1, wherein the circuitry is further configured to decode the encoded bitstream in units of a coding tree unit.
 7. The apparatus according to claim 1, wherein the circuitry is further configured to provide a mapping of the region in an enhancement layer to the region in a base layer.
 8. The apparatus according to claim 1, wherein the circuitry is further configured to provide a mapping of the region in a base layer to the region in an enhancement layer.
 9. The apparatus according to claim 1, wherein the video is encoded with independently decodable tiles and in one or more resolution layers.
 10. The apparatus according to claim 1, wherein the information further includes: an identified tile set, and inter-layer constrained tile sets supplemental enhancement information message that indicates that inter-layer prediction process is constrained such that no sample value outside each associated reference tile set, and no sample value at a fractional sample position that is derived using one or more sample values outside each associated reference tile set, is used for inter-layer prediction of a specific sample within the identified tile set.
 11. A method, comprising: decoding an encoded bitstream; and generating an image of a region based on information which indicates whether a value of each sample in a motion constrained tile set is the same as a value of a sample obtained in a case where all coding tree blocks of all pictures are decoded, and in a case where boundaries of the motion constrained tile set are treated as picture boundaries for the decoding, and the coding tree blocks that do not belong to the motion constrained tile set are not decoded, wherein the encoded bitstream includes the information, the information further indicates that an area outside the region is not to be displayed, the information includes one flag that applies to every tile, the information further includes flag information that indicates whether a last tile set includes a plurality of tiles that are not included in previous tile sets in a same message, and the last tile set is not be displayed, and the previous tile sets are specified prior to the last tile set.
 12. The method according to claim 11, wherein the information is included in a supplemental enhancement information message of the encoded bitstream.
 13. The method according to claim 11, further comprising receiving the encoded bitstream including a supplemental enhancement information message.
 14. The method according to claim 11, wherein the generation of the image comprises generating the image of the region including one or more tiles.
 15. The method according to claim 14, wherein the region includes the one or more tiles based on user selection.
 16. The method to claim 11, wherein the decoding of the encoded bitstream comprises decoding the encoded bitstream in units of a coding tree unit. 